general principles of seed production technology

PRINCIPLES OF SEED

PRODUCTION.

BySri. Roshan Parihar (Asst.Prof.)

TCB College of Agri.& Res. Station

Sarkanda ,Bilaspur,(C.G.)495001

• Genetic principles• Agronomic principles

General Principles of seed Production.

GENETIC PRINCIPLESDeterioration of Crop Varieties and Methods to prevent themVariety: It Is a group of plants having clear distinguished

characters which when reproduced either sexually or asexually retains these characters.

• The main aim of seed production is to produce genetically pure and good quality seed. But why/how the genetic purity of a variety is lost or deteriorated during seed multiplication.

• The several factors that are responsible for loss of genetic purity during seed production as listed by kadam (1942) are:

• 1. Developmental Variation• 2. Mechanical Mixtures• 3. Mutations

• 4. Natural Crossing• 5. Genetic drift• 6. Minor Genetic Variation• 7. Selective influence of Diseases• 8. Techniques of the Breeder• 9. Breakdown of male sterility• 10. Improper / defective seed certification

System

• 1. Developmental Variation :Due to difficult environment , soil and fertility condition , diff. climatic conditions ,diff elevations, hence reco. to grown on adapted areas and growing seacons.

• 2. Mechanical Mixtures : At the time of sowing due to seed drill, volunteer plant of the same crops, during harvesting and threshing operations. Seeds may get retained on the processing equipments. Precaution of rouging to done to prevent the mechanical admixtures.

• 3. Mutations : Not a serious cause in seed production,vegetatively propagated crops are genetically purified by the use of true to type stock.

• 4. Natural Crossing: introgression of genes from unrelated stock is the main cause of natural crossing. It occurs due to the folowing reasons.

– Natural crossing with undesirable types.– Natural crossing with diseased types.– Natural crossing with off type plants.

Seed production of hybrids may be get contaminated with the near by variety of the same crop however properly isolated, due to by breeding system of sp (such as A,B line),varietal mass, wind direction and pollinating agent.

• 5. Genetic drift : When seed is multiplied in large areas only small quantities of seed is taken and preserved for the next years sowing. Because of such improper sub-sampling allthe genotypes will not be represented in the next generation and leads to change ingenetic composition. This is called as genetic drift.

• 6. Minor Genetic variation: Released varieties may have small scale of genetic variation present at the time of release .when it goes under seed production selective enviromwent pressure has been removed and starts to show the changes and may finally affects the yield. Hence seed production of nucleus seed and breeder seed must be taken with utmost care to avoid such

• 7.Selective influence of Disease: New varieties may become susceptible to new races of pathogen and leads to out of date byt seed programme, hence proper crop protection must be applied to grow a healthy crop.

• 8. Techniques of the Breeder :cytogenetical irregularties, early or pre mature release of varieties.release of segregatigng stock as a variety,

• 9. Breakdown of male sterility:Generally in hybrid seed production if there is any breakdown of male sterility in may lead to a mixture of F1 hybrids and selfers.

• 10. Improper Seed Certification : It is not a factor that deteriorates the crops varieties, but is there is any lacuna in any of the above factors and if it has not been checked it may lead to deterioration of crop varieties.

Maintenance of Genetic Purity during seed Production• Horne (1953) had suggested the following methods

for maintenance of genetic purity;• 1. Control of seed source or Use of approved seed in

seed multiplication.– Seed classes of breeder , foundation or certified

seeds must be used.• 2.Preceding crop requirements :

– Providing isolation distance to prevent cross fertilization or mechanical mixtures of other varieties.

– Distance to be maintained for all the farm operations for genetic purity maintenance.

– Rouging of seed fields prior to planting and during the various stages prior to flowering.

• IN THE FIELD WHERE SEED PRODUCTION OF ANY CROP IS TO BE TAKEN THE SAME CROP COULD NOT BE GROWN IN PREVIOUS SEASON .

•Providing isolation distance to prevent cross fertilization or mechanical mixtures of other varieties.

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What is Isolation ?• Keeping the seed production plots

apart from fields of the same crop to avoid the risk of contamination by pollen from the neighboring fields. Isolation between seed plots can be effected by distances (spatial isolation) or time (temporal isolation).

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Types of Isolation

• Types of Isolation:• 1. Spatial Isolation• 2. Temporal Isolation• 3. Physical barrier

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What is Spatial Isolation

The spatial separation required between a seed field and other sources of genetic and mechanical contamination, especially between varieties of cross pollination.

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Spatial Isolation

•MORE THE EXTENT OF OUT CROSSING WIDER THE DISTANCE.

• HIGHER THE CLASS OF SEED WIDER THE DISTANCE. (BS v/s FS).

• IN HYBRID SEED PRODUCTION WIDER THE DISTANCE THAN THAT OF VARIETY(INBRED/PURELINE).

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2. Temporal Isolation• CROP OF SEED PRODUCTION SHOULD BE SOWN EARLY OR LATE BY A MARGIN OF 15-20 DAYS THAN NEIBOURING FIELDS OF SAME OR OTHER VARIETY TO PREVENT ENTRY OF FORGEIN POLLENS IN THE FIELD OF SEED PRODUCTION .

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3. Physical barrier• IN SURROUNDING OF CROP OF SEED PRODUCTION PARTICULARLY ON BUNDS CROP OF WELL PLANT HEIGHT AND DENSLY PLANTED SHOULD BE GROWN TO PREVENT ENTRY OF FORGEIN POLLENS IN THE FIELD OF SEED PRODUCTION .

What is Roguing ?• Roguing“The selective removal of

undesirable plants from a seed crop on the basis of visual field inspection, in order to improve one or more quality (genetic purity, disease free) attributes of the seed lot to be harvested"

(Laverack and Turner 1995).

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Rouging ---------

• Removal of noxious weeds (wild oat in wheat, and Argemone mexicana in Brassica species) that are liable to multiply with the seed crop, thus affecting future generations, may be regarded as part of roguing.

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Rouging ---------

• Rouging at all stages of the crop in the field is an essential requirement to maintain the variety purity as it was at the time of release/notification.

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Rouging ---------

• Sometimes rogue plants are not distinguishable before flowering, therefore, rouging should be done, as early as blooming starts.

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Rouging

• Doubt ful plants too should be rouged.

• The rogued plants should be removed from the field immediately after roguing and destroyed as they may survive for a few days and may spread their pollen.

• 3.Certification of seed crop by SCA Authorities to maintain genetic purity and quality.– Inspection of seed fields prior to

planting ,and approval of the Crop at critical stages for verification of genetic purity, detection of mixtures, weeds and seed borne diseases.

– Sampling and sealing of cleaned lots.

– Adopting generation system

What is Seed certification The main objective of seed certification is to make available seeds of good quality with 100 % pure genetic purity to farmers. To achieve this qualified and trained personnel from SCA (SEED CERTIFICATION AGENCIES)carry out field inspections at appropriate stages of crop growth.They also make seed inspection by drawing samples from seed lots after processing.

What is seed certification ?

• The SCA verifies for both filed and seed standards and the seed lot must confirm to get approval as certified seed.

• 4.Grow in adapted areas only to avoid genetic shifts in the variety.

• 5. Growing of samples with authentic stocks or Grow -out test for Periodic testing of varieties for genetic purity.

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GROW OUT TEST (GOT )

• Genetic purity of any variety is confirmed by carrying out through grow out test (GOT i.e. growing of progenies during off-season in the field) and electrophoresis . These tests are essential part of seed certification of hybrids and high valued seeds.

Electrophoresis

Genetic purity of any variety is confirmed by carrying out through molecular method of protein electrophoresis . Where protein bands are run on agarose gel alog with the reference band , if both test and reference band are same then genetic purity is confirmed.

SEPARATION AND DETECTION OF PROTEINS II

SDS-PAGE

SDS-PAGE(= sodium dodecylsulphate-polyacrylamide gel

electrophoresis)

-Method for separation of proteins according to their molecular weight

Outline of second part of the experiment

*Prepare polyacrylamide gels*Add diluted samples to the sample buffer

*Heat to 95C for 4 minutes*Load the samples onto polyacrylamide gel

*Run 200 volts for 30-40 minutes*Stain in Coomassie Blue stain

*Destain*Identify molecular markers, actin and myosin

in the separated proteins

Levels of Protein Organization

• Primary structure = linear chain of amino acids

• Secondary structure = domains of repeating structures, such as β-pleatedsheets and α-helices

• Tertiary structure = 3-dimensional shape of a folded polypeptide, maintained by disulfide bonds, electrostatic interactions, hydrophobic effects

• Quaternary structure = several polypeptide chains associated together to form a functional protein

-Proteins denatured by heating them in a sample buffer containing sodium dodecyl sulphate (SDS)

-The proteins no longer have any secondary, tertiary or quaternary structure

-Resultant proteins take on a rod-like shape and a uniform negative charge-to-mass ratio proportional to their molecular weights

How does an SDS-PAGE gel work?

•Negatively charged proteins move to positive electrode •Smaller proteins move faster

• Proteins separate by size

-

+

s-s

SDS, heat

proteins with

SDS

What is in the Sample Buffer?

*Tris buffer to provide appropriate pH*SDS (sodium dodecyl sulphate) detergent to

dissolve proteins and give them a negative charge

*Glycerol to make samples sink into wells*Bromophenol Blue dye to visualize samples

SDS-Polyacrylamide Gel Electrophoresis (SDS-PAGE)

•SDS (Sodium Dodecyl Sulfate) detergent

– solubilizes and denatures proteins– negative charge to proteins

•Heat denatures proteins

O

S

O

O

O

-

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH3

SDS

Why Use Acrylamide Gels to Separate Proteins?

• Acrylamide gel: Tight matrix

• Ideal for protein separation • Smaller pore size than agarose • Proteins much smaller than intact

chromosonal DNA-average amino acid = 110 Dalton

Protein Size• Size measured in daltons (Da) or kilodaltons (kDa)

• Dalton = atomic mass unit

= corresponds to mass of hydrogen

molecule (1.66 x 10 -24 gram)= defined also as 1/16 of the mass of an

atom of oxygen

• Average amino acid = 110 Da Average nucleotide pair = 649 Da

Gel Analysis

Lane 1. Kaleidoscope Markers 2. Shark 3. Salmon 4. Trout 5. Catfish

6. Sturgeon 7. Actin and Myosin Standard

Agronomic principles of seed prod.

Selection of a suitable Agro* Climatic region:1.Photoperiod.2.Temperature.3.Rainfall.(Moderate)4.Humidity. (Moderate) 5.Sun Insolation.(Dry sunny days)6.Wind velocity.

•Excessive dew and rain cause hinderance in pollination.•Too high temp cause dessication of pollen and resulted poor seed set.•Hot and dry weather in case of vegetable , legumes fail to seed set effectively and leads to seed less fruits.•Vegetables requires cool climate and low humidity for flower and pollination.

• For cross pollinated crops adequate wind velocity must be required to complete pollin.

• Oilseed crops can tolerate high temp. but rise of terminal heat may leads to force maturity resulted small seed size.

• So very cold temp also damage seed quality in early phases of seed maturation.

• Seed crops for rabi season must not be grown on such areas where winter rains prevailed because it may cause seed quality deterioration at the harvesting time and also make harvesting a big problem.

• Damp and humid weather increase the disease and pest attack on the field as well as storage site.

Selection of seed plot

1.Soil texture and fertility.2.Site free from volunteer plants,

weeds, other crop plants.3.Site must be free from soil

borne disease and pests.4.Preceding crop must not be

same.5.Site must be levelled and

irrigation facilities must present

isolation of seed plot

1.Isolation of distance must be maintained as per the requirement.

2.If distance isolation is not maintained than Temporal or Time isolation must be practices by altering the sowing date by differential planting.

3.On a small scale of Nucleus or Breeder seed production barrier isolation must be maintained.

• Land for seed crop must be well prepared, well levelled so that water stagnation must not take place.

• Good land status enhance good seed germination,field emergence and stand establishment.

• Well pulverised seed bed and trash must be picked up and removed before sowing,

Preparation of land

• Variety adapted to the agro-climatic regions.

• High yielder variety.• Variety with exellent features

viz.quality,earliness,resistance etc.

Selection of variety

• Seeds of appropriate class must be brought with cash memo.

• Check out the seals and tags are remain intact and bags are not torned.

• Check out the details mentioned on the label with full assurance.

• Cash memo must be kept with care for further verification.

Verification of Seed source

• Revolving drum used for the treatment of seeds.

• Chemical seed treatment.• Bacterial inoculation of seeds.

a. By drum method.b. By the use of vaccum seed treater on USA

, on which seeds are first made permeable and then liquid suspension of bacterial inoculation must be applied to each seed under vaccum creation forces the entrance of bacteria into the seed.

Seed treatment

• Seed treatment to break dormancy.a. Hard seeded crops are water

soaked.b. Mechanical scarification must be

done for seed coat breakage.c. Acid scarification must be done for

crops where this the only method applied viz.seeds soaked in 95 % sulphuric acid for 15-60 minutes.

Time of sowing / Seed rate

• Should be sown on normal sowing time with adequate moisture enhances germination.

• Low seed rates are preferred for easy roguing operations and inspection.

• Broadcasting is also used.• Seed drill method is preferred to ensure

depth for germination.• Line sowing favours roguing, inspection

and interculture operations by mechanical methods also.

• Small seeds are planted shallow,while large seeds are planted deeper.

• In sandy, warm and dry soils seeds should be sown on high depth.

Method of sowing.

• Vegetative stage /pre flowering stage based on height, colour of vegetation,leaf size,shape , orientation or diseased or malformed plant.

• Flowering stage roguing based on emergence of panicle characters and uprooting of such plants.

Roguing

• Flowering stage roguing is equally important in case of hybrid crops. Where in a male sterile line (A line) a plant of male fertile line (B line) is present. Such B Line plants are called as POLLEN SHEDDERS and it must be rogued out at flowering stage.

• Maturity stage roguing is important and it leads to removal of defective ear heads viz. off textured, off coloured,diseased or malformed etc.

• In case of cross pollinated crops if a bee hive is present in the close proximity of the seed farms it leads to higher seed set.

Supplementary pollination

• Weeds may increase the chances of admixtures.

• Weed plants are the source of disease host .

• Noxious weeds pose a serious set back to seed purity if not controlled.

• Weed crop compete with the seed crop for food and space.

Weed control

• Seed crop must be seed treated for systemic disease.

• As soon as pest attack seen control must be applied to retain the healthy plant,

• Diseased and pest infested plant are unable to make food efficiently and hence should be rogued out.

Disease and insect control

• Seed crop must be supplied with nitrogen to maintain their status green.

• More nitrogen must increase the succulence and delay the maturity.

• When yellowing occurs on the lower leaves and upper leaves are green it must be supplied.

Nutrition

• In case of severe nitrogen shortage leaves will turn brown and die.

• On early stage of crop don’t supply too much nitrogen, may increase the height, reduce flowering and lodging too happen.

• As the crop proceeds toward flowering provide the second split of nitrogen.

• Along with the first split of N , P and k must be given as a basic dose.

• Phosphorous is associated with root growth, straw length,fruiting , seed development ,plant maturity and disease resistance.

• Pottassium is associated with photosynthetic ability of the plant ,flowering and seed development.

• K deficiency leads to a general loss of dark green colour, straw weakning , severe deficiency leads to produce bronze to yellow discolouration along the edges of older lower leaves.

• As the crop needs water it must be supplied .

• To be supplied at all the critical stages of crop.

• Surface irrigation method of water application with check basin must be used for the judicious use of water.

Irrigation scheduling of seed crops

Assessment of Harvesting time

• Harvesting time is one of the important factors that influence the planting value of seeds.

• The moisture content of seeds is an important consideration in deciding the time of harvesting.

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HARVESTING----2

Early harvest (pre-mature) causes:1. High number of partially filled and immature seeds with high moisture content.

2. Seed quality such as longevity and field emergence depressed.

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Maximum germination and vigor is recorded at physiological maturity (Harrington 1972).

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HARVESTING

Physiological maturity denotes the stage of development when the seed reaches its maximum dry weight and marks the end of the seed-filling period.

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HARVESTING-6

Optimum time or stages of harvest in some crops grown

for seedCrop Time / Stage of harvest

• Rice 27 Days After Anthesis

• Sorghum 30-35 Days After Anthesis

• Sorghum 35-40 Days After Anthesis (late varieties)

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H A R V E S T I N G -5

OPTIMUM STAGES OF HARVEST IN SOME CROPS GROWN FOR SEED PRODUCTION

• Arhar 25 Days After Anthesis

• Mungbean 25 Days After flowering

• Toria 70-100 Days After Sowing

• Soybean 100-104 Days After Sowing

• Cotton 55-60 Days After anthesis

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Threshing 1

• Before the threshing of harvest of seed production plot threshing floor/ thresher must be clean thoroughly to avoid any physical impurities and or admixture of seeds of any crop and weeds.

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Threshing II

• Threshing of harvest of seed production plot Should be done first then commercial crop.

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Storage of produced seeds --------

• Before storing, seeds must be sun dried properly to maintain moisture content of seeds.

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Packing material used for seed storage plays important role to maintain seed’s longevity during storage.

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Under ambient conditions (room temperature) use of air permeable containers viz. cotton cloth or gunny begs, as compare

to polythene bags, is better.These should be stored in dry

and cool place.

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• In storage optimum condition conditions particularly temperature and RH% must be maintained.

• Preventive control measures against storage pest must be taken.

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• Herrington (1959) proposed thumb rules for safer storage of seed by

maintaining temperature and RH% in storage as;

1.“ THE SUM OF TEMPERATURE (0F) and RH% IN STORAGE MUST BE 100±2 ”

Examples inculdes such as 50 % RH and temp at 50 (0F) or 60 % RH and 40 (0F) are found suitable for maintain seed quality of maize for a period of one year or more.

2. 1 % Reduction in moisture content of seed doubles the seed longevity.

general principles of seed production technology

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